Treating residual liquors accruing from the treatment of cellulose material



Patented Mar. 4, 193i) UNITED STATES PATENT OFFICE PIERRE ALFRED BARBOU,OI PARIS, FRANCE, ASSIGNOR TO SOCIE'IE BARBOU 66 CIE.,

OF PARIS, FRANCE, A FRENCH CORPORATION TREATING RESIDUALLIQUORS-ACCBUING rnou THE TREATMENT or CELLULOSE MATERIAL No Drawing.Application filed April 5,1927, Serial No. 31,282, and; in France April21, 1926. v

It is known that cellulose material treated at 140 C. with an aqueoussolution of sodium bisulphite, is thereafter hydrolyzed to yield purecellulose, the non-cellulose elements of the vegetable material beingdissolved in the available for recovering the sodium sulphite.

lyes in which the said material is boiled. This lixiviating methodhowever has found no industrial use because of its high cost which isdue to the circumstance that no inexpensive and simple method washitherto at 140 C. upon two molecules of lignin to yield an alcohol andan acid organic compound. It is-likewise known that the acid moleculereacts upon-sodium sulphite to form a .sulphonated compound, the valencyof the 5 S0 group being saturated by an'atom of sodium andthe acidfunction of the organic acid formed by hydrolysis being saturated by thesecond atom of sodium contained in the molecule of sodium sulphite,

The residual lyes or liquors accruing from -the boiling of vegetablematter with sodium sulphite contain therefore, in solution,- an

- alcohol and a sulphonated compound (withwhich two atoms of sodiumare'combined.

The sulphonated molecule is dissociated when the residual liquors aretreated for example with any alkaline-earth base such as concentratedmilk of lime. The SO group fixed to this molecule combines with the limeto yield insoluble calcium sulphite while the sodium atoms combine withthe hydroxyl "ions of the calcium-toform caustic soda.

u on the organo-sodium molecule, an insolub e organo-calcium componentis formed, together with a mixture of sodium sulphite and bisulphite.The bisulphite formed is tion) in the form of Na sO neutralized by anaddition of NaOH so that all the S0 and N 21 0 elements contained in theresidual liquor are thus obtained (in solu- The lows:

1. The lye or liquor accruing from the boiling of vegetable matter withsodium sulphite process, is carried into practice as folis treated withlime at 75 C. in an open or drawn ofi' and transferred to a further,open or closed container.

4. The correct amount of calcium bisul- 'phite solution is now added tothe liquor.

The mixture -is then pneumatically or me chanically agitated for a fewminutes and thereafter allowed to stand."

5. After an hour the clear supernatant liquid is drawn 0E andneutralized with caustic soda to obtain a solution of sodium sulphitewhich may be usedfor further lixiviating op erations.

A satisfactory result is obtained only by using the reagents in accuratequantities. Adding too much lime in the course. of the first operationproduces, in addition to sodium sulphite, an organo-calcium compoundwhich does not precipitate and persistently. clouds the liquor. Again,adding too much calcium bisulphite causes the liquor to becomeover-acid, entailing theuse of an undue quantity of soda forneutralization purposes.

The proportion in which the reagent is to be used is ascertained asfollows:

The total amount of sodium to be recovered from the residual liquors ismeasured by incineration with the exclusion of air. In the course oftheincineratiug operation the sulphur of the sulphonated group and theatoms of sodium combined with the organic molecule, combine with oneanother to. form sodium sulphide which is titrated by evaluation in theform of NaOH in any suitable and known way. If A is the quantity foundin the form of NaOH, the amount X of $0 com tained inthe residualliquors is given by the formula X since 80 grammes of lime is given bythe formula Y= The proportion of S0 to be added in the form of calciumbisulphite to the liquor treated-with lime for sulphiting the Naelements, is ascertained as follows: The amount of Na (determined in theform of NaOH in the course of the first measurement) contained in theresldual liquor, 1s known, and since 810 grammes of NaOH require 64grammes of S0 to form Na SO the amount Z of S0 to be added to the liquoris given by the formula, Z A X 64 S0 contained in the calcium bisulphitesolution to be used, the volume of this liquor to be placed in reactionis easily determined.

Calcium carbonate or any other alkaliearth carbonate may be used toneutralize the sulphonated group fixed to the organic molecule, but thereaction is not so complete, in that reaction equilibrium is rapidlyreached between CaCO CO and SO ,zthe reaction being detrimentallyaffected thereby. The industrial scope of the process according totheinvention covers the manufacture of cellulose for making paper or asinitial material for artificial silk and artificial Wool. The cost ormanufacture of these materials is Knowing the total percentage ofconsiderably lowered'because of the recovery of chemical substances andorganic matter of all kinds.

Claims:

1. A. process for recovering S0 and Na O contained in residual liquorsderived from the boiling of cellulose material, comprising a treatmentof the said residual liquors, accruing from the boiling of vegetablematter in a sodium sulphite solution, with an alkalineearth base toproduce caustic soda, an organosodium compound and an insolublealkalineearth metal sulphite, and treating the liquors thus obtainedwith a bisulphite to form a sodium sulphite, this compound being formedtogether with the precipitation of organic matter in the form oforgano-metallic combingtions corresponding to the bisulphites use 2. Aprocess for recovering S0 and Na O contained in residual liquors derivedfrom the boiling of cellulose materiahcomprising treating the saidresidual liquors, accruing from the boiling of vegetable matter in asodium sulphite solution with an alkalineeartlibasetoproducecausticsoda, an organosodium compound, an insolublealkaline-earth metalsulphite, treating the liquors thus obtained with abisulphite to formfla sodium sulphite, this compound being formedtogether with the precipitation of organic matter in the form oforgano-metallic combinations corresponding to thebisulphites used,

and converting the insoluble alkaline-earth metal sulphite obtained intoalkaline-earth metal bisulphite by treating the decantation sedimentwith sulphurous anhydride.

In testimony whereof I aflix my signature PIERRE ALFRED BARBOU.

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